Well, it must have had dual meanings or something.
Looks like it’s had essentially the same meaning for hundreds of years.
They did rename the story for the movie version the next year.
# Bahama Passage (1941), starring Sterling Hayden and Madeleine Carroll, was filmed on Grand Turk and Salt Cay. It was based on the book Dildo Cay by Nelson Hayes.
http://en.wikipedia.org/wiki/Turks_and_Caicos_Islands#References
A girl, Carol whom the audience is quickly informed “has been around,” and her father arrive to take over the business management of an island in the Bahamas...
http://www.imdb.com/title/tt0033372/plotsummary
Perhaps the professor will include the review in next year’s syllabus.